Probing the enigmatic Fermi surface of SmB6 by low-energy electrodynamics

用低能电动力学探测 SmB6 的神秘费米面

• 批准号: 419885010
• 负责人: Dr. Marc Scheffler
• 金额: --
• 依托单位: 1. Physikalisches Institut
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/419885010?language=en
• 关键词: Probing; enigmatic; Fermi; surface; SmB6

In the field of correlated electron physics, samarium hexaboride (SmB6) is one of the most studied and yet most puzzling materials. Traditionally considered a Kondo insulator, SmB6 was more recently interpreted as the first topological insulator with electronic correlations. This notion calls for a two-dimensional Fermi surface caused by the charges of the topological surface states, but recent high-profile quantum-oscillation results on SmB6 are gravely conflicting: one study reported signatures for a two-dimensional Fermi surface whereas another indicated a three-dimensional Fermi surface. The latter result cannot be reconciled with SmB6 being truly insulating in the bulk at low temperature, and it has sparked a plethora of new theoretical concepts, some of them invoking exotic quasiparticles quite different from regular electrons in solids.In this project we want to elucidate the nature of the Fermi surface of SmB6 by means of low-energy electrodynamics. In particular, we want to detect and characterize the cyclotron resonance of SmB6. This will be an independent experimental access to the properties of the Fermi surface, regardless of whether the latter is two- or three-dimensional. In conventional solids, cyclotron resonance is probed by applying a microwave electric field to a sample in a static magnetic field. For the case of SmB6, there is no consensus on the values of effective mass and scattering rate of the relevant mobile quasiparticles, and it is not even clear whether they are charge carriers or neutral. Therefore, at this stage, we cannot predict at which combination of magnetic field and excitation frequency and below which temperature the cyclotron resonance of SmB6 will be observable. Hence we will use a variety of experimental techniques (at frequencies between 45 MHz and 1.3 THz, at magnetic fields up to 8 T, at temperatures down to 20 mK, and with option to selectively excite with either electric or magnetic high-frequency field) to unriddle the electrodynamic response of SmB6. These experiments in extremely wide parameter ranges will reveal key information on the Fermi surface via detection of cyclotron resonance, and in addition they will help us to answer another puzzle in the properties of SmB6, namely whether the previously reported THz conductivity of SmB6, which is much higher than expected from the established dc conductivity, is caused by the same enigmatic quasiparticles that possibly generate the three-dimensional Fermi surface of SmB6.

在相关的电子物理学领域，撒克萨博酯（SMB6）是研究最多，但最令人困惑的材料之一。传统上，SMB6在传统上被认为是围绕的绝缘子，最近被解释为第一个具有电子相关性的拓扑绝缘子。该概念要求由拓扑表面状态的电荷引起的二维费米表面，但是最近对SMB6的备受瞩目的量子振荡结果是严重冲突的：一项研究报道了二维费米表面的签名，而另一个研究表明另一种三维费米表面。后者的结果不能与SMB6在低温下真正绝缘构成，并且它引发了许多新的理论概念，其中一些人唤起了与固体中的常规电子截然不同的异国情调的准颗粒。特别是，我们要检测和表征SMB6的回旋共振。这将是对费米表面特性的独立实验访问，无论后者是二维还是三维。在常规固体中，通过将微波电场应用于静态磁场中的样品来探测回旋子共振。对于SMB6，关于相关移动准粒子的有效质量和散射率的值尚无共识，甚至还不清楚它们是荷载还是中性。因此，在此阶段，我们无法预测磁场和激发频率的组合以及在哪种温度以下，可以观察到SMB6的回旋谐振。因此，我们将使用各种实验技术（在45 MHz和1.3 THz之间的频率下，在高达20 MK的磁场上，在降至20 MK的磁场上，并且可以选择用电气或磁性高频场选择性地激发SMB6的电动力学响应。 These experiments in extremely wide parameter ranges will reveal key information on the Fermi surface via detection of cyclotron resonance, and in addition they will help us to answer another puzzle in the properties of SmB6, namely whether the previously reported THz conductivity of SmB6, which is much higher than expected from the established dc conductivity, is caused by the same enigmatic quasiparticles that possibly generate the three-dimensional Fermi surface of SMB6。